WIP checkpoint: Friends/follow/block models + Alembic migration

backend/app/models/__init__.py

@@ -2,5 +2,17 @@ from app.models.user import User
 from app.models.session import Session
 from app.models.world import World
 from app.models.asset import Asset
+from app.models.friendship import Friendship, FriendshipStatus
+from app.models.follow import Follow
+from app.models.block import Block
 
-__all__ = ["User", "Session", "World", "Asset"]
+__all__ = [
+    "User",
+    "Session",
+    "World",
+    "Asset",
+    "Friendship",
+    "FriendshipStatus",
+    "Follow",
+    "Block",
+]

backend/app/models/block.py

@@ -0,0 +1,48 @@
+"""Block model: a hard deny that also hides content and prevents DMs."""
+
+from sqlalchemy import CheckConstraint, Column, DateTime, ForeignKey, Integer, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Block(Base):
+    __tablename__ = "blocks"
+    __table_args__ = (
+        UniqueConstraint(
+            "blocker_id",
+            "blocked_id",
+            name="uq_blocks_blocker_blocked",
+        ),
+        CheckConstraint(
+            "blocker_id <> blocked_id",
+            name="ck_blocks_no_self",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    blocker_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    blocked_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    blocker = relationship(
+        "User",
+        foreign_keys=[blocker_id],
+        back_populates="blocks_given",
+    )
+    blocked = relationship(
+        "User",
+        foreign_keys=[blocked_id],
+        back_populates="blocks_received",
+    )

backend/app/models/follow.py

@@ -0,0 +1,48 @@
+"""Follow model: a one-way relationship requiring no approval."""
+
+from sqlalchemy import CheckConstraint, Column, DateTime, ForeignKey, Integer, UniqueConstraint
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Follow(Base):
+    __tablename__ = "follows"
+    __table_args__ = (
+        UniqueConstraint(
+            "follower_id",
+            "followed_id",
+            name="uq_follows_follower_followed",
+        ),
+        CheckConstraint(
+            "follower_id <> followed_id",
+            name="ck_follows_no_self",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    follower_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    followed_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    follower = relationship(
+        "User",
+        foreign_keys=[follower_id],
+        back_populates="follows_given",
+    )
+    followed = relationship(
+        "User",
+        foreign_keys=[followed_id],
+        back_populates="followers",
+    )

backend/app/models/friendship.py

@@ -0,0 +1,74 @@
+"""Friendship model: a one-directional request that becomes mutual on accept."""
+
+from sqlalchemy import (
+    CheckConstraint,
+    Column,
+    DateTime,
+    ForeignKey,
+    Integer,
+    String,
+    UniqueConstraint,
+)
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class FriendshipStatus:
+    """String values for the friendship.status column."""
+
+    PENDING = "pending"
+    ACCEPTED = "accepted"
+
+
+class Friendship(Base):
+    __tablename__ = "friendships"
+    __table_args__ = (
+        UniqueConstraint(
+            "requester_id",
+            "addressee_id",
+            name="uq_friendships_requester_addressee",
+        ),
+        CheckConstraint(
+            "requester_id <> addressee_id",
+            name="ck_friendships_no_self",
+        ),
+        CheckConstraint(
+            "status IN ('pending', 'accepted')",
+            name="ck_friendships_status",
+        ),
+    )
+
+    id = Column(Integer, primary_key=True, index=True)
+    requester_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    addressee_id = Column(
+        Integer,
+        ForeignKey("users.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    status = Column(
+        String(20),
+        nullable=False,
+        default=FriendshipStatus.PENDING,
+        server_default=FriendshipStatus.PENDING,
+    )
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
+
+    requester = relationship(
+        "User",
+        foreign_keys=[requester_id],
+        back_populates="friendships_sent",
+    )
+    addressee = relationship(
+        "User",
+        foreign_keys=[addressee_id],
+        back_populates="friendships_received",
+    )

backend/app/models/user.py

@@ -19,3 +19,41 @@ class User(Base):
     sessions = relationship("Session", back_populates="user", cascade="all, delete-orphan")
     worlds = relationship("World", back_populates="owner")
     assets = relationship("Asset", back_populates="owner")
+
+    # Social graph
+    sent_friend_requests = relationship(
+        "Friendship",
+        foreign_keys="Friendship.requester_id",
+        back_populates="requester",
+        cascade="all, delete-orphan",
+    )
+    received_friend_requests = relationship(
+        "Friendship",
+        foreign_keys="Friendship.addressee_id",
+        back_populates="addressee",
+        cascade="all, delete-orphan",
+    )
+    following = relationship(
+        "Follow",
+        foreign_keys="Follow.follower_id",
+        back_populates="follower",
+        cascade="all, delete-orphan",
+    )
+    followers = relationship(
+        "Follow",
+        foreign_keys="Follow.followed_id",
+        back_populates="followed",
+        cascade="all, delete-orphan",
+    )
+    blocks_issued = relationship(
+        "Block",
+        foreign_keys="Block.blocker_id",
+        back_populates="blocker",
+        cascade="all, delete-orphan",
+    )
+    blocks_received = relationship(
+        "Block",
+        foreign_keys="Block.blocked_id",
+        back_populates="blocked",
+        cascade="all, delete-orphan",
+    )